1. Field of the Invention
This invention relates, in general, to an analytic device including a power source.
2. Description of Related Art
Modern analytic systems are typically powered by electrical current and voltage. Although subcomponents of the system may be powered with a primary system power, the power must be transformed for each component to a desired voltage or current. Some components require a regulated current or voltage at very low levels, within a narrow variation range, and/or with low noise, which can be difficult to produce based on the primary system power.
In the fields of biochemistry and analytical chemistry, laboratory researchers sometimes analyze samples based on small differences in electrochemical responses. For this reason, electrochemical detectors generally require a fixed, low-power input and exhibit a high sensitivity to minute fluctuations and variations in electrical current or voltage. An electrochemical detector may employ a reference electrode combination operated by application of a biasing potential. The bias voltage is applied between the two electrodes where one of the electrodes carries the output signal of the electrochemistry detector. In turn, the detector is connected to a recording device that provides a permanent record of the events which have taken place at the active surface of the detector.
A significant problem in biomedical and biochemical investigations is the ability to monitor the minute amounts (e.g. picogram, or femtogram level) of biologically active compounds. This translates into a need for analytic systems with sufficient sensitivity for the target compounds, linearity over the physiologically relevant concentration range, and compatibility with the rest of the system components. The system generally requires a fixed and accurate power supply. Even minor variations from the desired voltage can cause drastic performance errors.
Another important concern with sensitive electrical equipment is the reduction or elimination of noise attributed to the power supply. In the example of detector electrodes, noise can be especially troublesome. The detector electrodes represent relatively high impedance, which mandate particularly high insulation of the biasing power supply in order to maintain sufficient noise performance. By contrast, other research components are typically powered by high voltage and are relatively insensitive to noise and voltage fluctuations. A problem occurs when the high power source introduces noise to more sensitive components. Small variations, errors, and noise from the power supply can cause large errors in the accuracy of the device and system. Greater variations in the power supply output consequently limit the sensitivity of the powered device.
One method of powering electrochemical detectors is with a conventional AC power supply. An AC power supply is typically used in combination with a transformer to convert the system power to a fixed biasing voltage for the detectors. AC power supplies, however, inherently produce noise and thus are unsuitable for sensitive electrical components.
Another method of powering electrochemical detectors is with a conventional DC/DC power supply. Similar to AC power supplies, a conventional DC/DC power supply typically injects a significant level of switching signal noise into the sensor circuit. Similar problems are observed when a DC/DC power supply is employed to power a front-end amplifier stage connected to floating electrodes. Good insulation and power noise separation is required for effective operation. It has been found that a conventional DC/DC power supply generally provides unacceptable errors in the biasing voltage and/or injects too much noise into the system when powering sensitive equipment like electrochemical detectors.
In addition, especially in fluid environments, conventional power supplies present the problem of how to ground the devices without cross-talk. In some cases, such as when working with flammable compounds, the wiring and open contacts of traditional power sources even present safety hazards.
Another method for powering system components employs a separate and self-contained power source, such as a standard battery. Standard electrochemical batteries reduce the risk of introducing noise to the system. But batteries present several drawbacks. For one, users prefer that the system only use one power source. Preferably the system is plugged into a constantly available power source such as an electrical outlet. Batteries also present their own unique problems like slow discharge and the need for manual replacement. The system typically has to be designed to account for electrical drift as the battery ages. Batteries also take up space, which can be problematic for some applications. Additionally, batteries can not be turned on and off.
In light of the foregoing, it would be beneficial to have methods and apparatuses which overcome the above and other disadvantages of known power supplies.
It would be beneficial to provide a power supply that can provide small voltages within a range sufficient for highly sensitive equipment. It would be beneficial to provide an improved power supply for use with biomedical and biochemical testing and analytical equipment.
It would be beneficial to provide a power supply that provides a constant and accurate current or voltage. It would be beneficial to provide a power supply with minimal noise. It would be beneficial to provide a method and device for providing a consistent, insulated voltage or current.
It would be beneficial to provide a power supply that integrates with existing systems and does not require a separate power connection. It would be beneficial to provide a power supply that reduces or eliminates grounding problems. It would be beneficial to provide a power supply that is floating and can be provided in different parts of an electrical system. It would be beneficial to provide a power supply that can be turned on and off.
It would be beneficial to provide a power source integrated with an analytical detector.
These and other advantages are provided by the devices and methods of the present invention.